Targeting Lipids Differentially Regulated in Settings of Physiological Cardiac Hypertrophy and Disease

The heart enlarges in response to stress such as cardiovascular disease. This is considered “bad” enlargement/growth as it typically progresses to heart failure. “Good” enlargement however, occurs in response to exercise and this is known to be protective. There are many defining traits between good and bad heart enlargement, but little is known about the regulation of lipids. In this thesis, approximately 600 lipids were profiled in various mouse models of good and bad heart enlargement. Differential regulation of lipids were identified, and treatment strategies to modulate specific lipids were conducted. Targeting lipids as a therapeutic strategy warrants further study

Lipidomic Profiles of the Heart and Circulation in Response to Exercise versus Cardiac Pathology: A Resource of Potential Biomarkers and Drug Targets

Summary: Exercise-induced heart growth provides protection against cardiovascular disease, whereas disease-induced heart growth leads to heart failure. These distinct forms of growth are associated with different molecular profiles (e.g., mRNAs, non-coding RNAs, and proteins), and targeting differentially regulated genes has therapeutic potential for heart failure. The effects of exercise on the cardiac and circulating lipidomes in comparison to disease are unclear. Lipidomic profiling was performed on hearts and plasma of mice subjected to swim endurance training or a cardiac disease model (moderate or severe pressure overload). Several sphingolipid species and phospholipids containing omega-3/6 fatty acids were distinctly altered in heart and/or plasma with exercise versus pressure overload. A subset of lipids was validated in an independent mouse model with heart failure and atrial fibrillation. This study highlights the adaptations that occur to lipid profiles in response to endurance training versus pathology and provides a resource to investigate potential therapeutic targets and biomarkers. : Tham et al. utilized a HPLC-ESI/MS/MS targeted lipidomics approach to show distinct remodeling of the cardiac and plasma lipidomes in response to exercise in comparison to heart disease stimuli. Differentially altered lipids were validated in a model with heart failure and atrial fibrillation and represent potential biomarkers and drug targets. Keywords: lipids, heart, exercise, physiological hypertrophy, pathological hypertrophy, atrial fibrillation, phospholipids, sphingolipids, biomarkers, treatmen

Silencing of miR-34a attenuates cardiac dysfunction in a setting of moderate, but not severe, hypertrophic cardiomyopathy

Therapeutic inhibition of the miR-34 family (miR-34a,-b,-c), or miR-34a alone, have emerged as promising strategies for the treatment of cardiac pathology. However, before advancing these approaches further for potential entry into the clinic, a more comprehensive assessment of the therapeutic potential of inhibiting miR-34a is required for two key reasons. First, miR-34a has ∼40% fewer predicted targets than the miR-34 family. Hence, in cardiac stress settings in which inhibition of miR-34a provides adequate protection, this approach is likely to result in less potential off-target effects. Secondly, silencing of miR-34a alone may be insufficient in settings of established cardiac pathology. We recently demonstrated that inhibition of the miR-34 family, but not miR-34a alone, provided benefit in a chronic model of myocardial infarction. Inhibition of miR-34 also attenuated cardiac remodeling and improved heart function following pressure overload, however, silencing of miR-34a alone was not examined. The aim of this study was to assess whether inhibition of miR-34a could attenuate cardiac remodeling in a mouse model with pre-existing pathological hypertrophy. Mice were subjected to pressure overload via constriction of the transverse aorta for four weeks and echocardiography was performed to confirm left ventricular hypertrophy and systolic dysfunction. After four weeks of pressure overload (before treatment), two distinct groups of animals became apparent: (1) mice with moderate pathology (fractional shortening decreased ∼20%) and (2) mice with severe pathology (fractional shortening decreased ∼37%). Mice were administered locked nucleic acid (LNA)-antimiR-34a or LNA-control with an eight week follow-up. Inhibition of miR-34a in mice with moderate cardiac pathology attenuated atrial enlargement and maintained cardiac function, but had no significant effect on fetal gene expression or cardiac fibrosis. Inhibition of miR-34a in mice with severe pathology provided no therapeutic benefit. Thus, therapies that inhibit miR-34a alone may have limited potential in settings of established cardiac pathology

Therapeutic silencing of miR-652 restores heart function and attenuates adverse remodeling in a setting of established pathological hypertrophy

Expression of microRNA-652 (miR-652) increases in the diseased heart, decreases in a setting of cardioprotection, and is inversely correlated with heart function. The aim of this study was to assess the therapeutic potential of inhibiting miR-652 in a mouse model with established pathological hypertrophy and cardiac dysfunction due to pressure overload. Mice were subjected to a sham operation or transverse aortic constriction (TAC) for 4 wk to induce hypertrophy and cardiac dysfunction, followed by administration of a locked nucleic acid (LNA)-antimiR-652 (miR-652 inhibitor) or LNA control. Cardiac function was assessed before and 8 wk post-treatment. Expression of miR-652 increased in hearts subjected to TAC compared to sham surgery (2.9-fold), and this was suppressed by ∼95% in LNA-antimiR-652-treated TAC mice. Inhibition of miR-652 improved cardiac function in TAC mice (fractional shortening:29±1% at 4 wk post-TAC compared to 35±1% post-treatment) and attenuated cardiac hypertrophy. Improvement in heart function was associated with reduced cardiac fibrosis, less apoptosis and B-type natriuretic peptide gene expression, and preserved angiogenesis. Mechanistically, we identified Jagged1 (a Notch1 ligand) as a novel direct target of miR-652. In summary, these studies provide the first evidence that silencing of miR-652 protects the heart against pathological remodeling and improves heart function.—Bernardo, B. C., Nguyen, S. S., Winbanks, C. E., Gao, X.-M., Boey, E. J. H., Tham, Y. K., Kiriazis, H., Ooi, J. Y. Y., Porrello, E. R., Igoor, S., Thomas, C. J., Gregorevic, P., Lin, R. C. Y., Du, X.-J., McMullen, J. R. Therapeutic silencing of miR-652 restores heart function and attenuates adverse remodeling in a setting of established pathological hypertrophy

Echocardiography data of control and TAC mice at baseline and four weeks post-TAC.

<p>BW, body weight; LV, left ventricular; LVPW, LV posterior wall thickness; IVS, interventricular septum thickness; LVEDD, LV end-diastolic dimension; LVESD, LV end-systolic dimension; FS, fractional shortening; EF, ejection fraction. Data are shown as mean ± SEM. One way ANOVA followed by Fisher’s Post hoc Test. *P&lt;0.05 vs. baseline of same group and control at same time point, †P&lt;0.05 vs. TAC moderate at same time point.</p

Morphological data for control and TAC moderate and severe mice following four weeks of pressure overload and eight weeks after treatment with LNA-control or LNA-antimiR-34a.

<p>BW: body weight, HW: heart weight, AW: atria weight, LW: lung weight, TL: tibia length, HW/TL: heart weight/ tibia length ratio, AW/TL: atria weight/ tibia length ratio, LW/TL: lung weight/ tibia length ratio. Data are shown as mean ± SEM. One-way ANOVA followed by Fisher’s post-hoc test (comparing 5 groups): *P&lt;0.05 vs. control, †P&lt;0.05 vs. control, ‡P&lt;0.001 vs. control, §P&lt;0.05 vs. TAC LNA control of the same group, ∥P&lt;0.05 vs. TAC-moderate of the same treatment group. One-way ANOVA followed by Fisher’s post-hoc test (comparing TAC moderate groups to control, i.e. 3 groups only): #P&lt;0.05 vs. control, **P&lt;0.05 vs. TAC LNA control.</p

Analysis of miR-34a target gene or protein expression.

<p>(A) Representative Western blots and quantification of VEGF-A and VCL relative to GAPDH in hearts of control (con), TAC moderate (mod), TAC severe (sev) mice dosed with either LNA-control (c) or LNA-antimiR-34a (a). N = 3–5 per group. ∧P&lt;0.05 vs. control when using 1 way ANOVA followed by Fisher’s Post Hoc test on severe group only. (B) qPCR analysis of <i>Sirt1, Sema4b</i>, <i>Vegfb, Pofut1,</i> PNUTS <i>(Pppr10)</i>, <i>Notch 1</i> and Cyclin D1 <i>(Ccnd1)</i> relative to <i>Hprt1</i>. N = 3–5 per group. ∧P&lt;0.05 vs. control when using 1 way ANOVA followed by Fisher’s Post Hoc test on control and TAC severe groups only (comparing three groups).</p

Expression of miR-34a, miR-34b and miR-34c in control and TAC mice.

<p>qPCR of miR-34a, miR-b and miR-34c in hearts of control, TAC moderate and TAC severe mice. N = 3–5 per group. *P&lt;0.05 vs. control, †P&lt;0.05. 1 way ANOVA followed by Fisher’s Post Hoc test.</p

Echocardiography data of control and TAC mice at baseline, four weeks post-TAC and eight weeks after treatment with either LNA-control or LNA-antimiR-34a.

<p>BW, body weight; LV, left ventricular; LVPW, LV posterior wall thickness; IVS, interventricular septum thickness; LVEDD, LV end-diastolic dimension; LVESD, LV end-systolic dimension; FS, fractional shortening.</p><p>Data are shown as mean ± SEM. One way ANOVA followed by Fisher’s Post hoc Test.</p><p>*P&lt;0.05 vs. baseline of same group and control at same time point, †P&lt;0.05 vs. TAC LNA control of same group at same time point, ‡P&lt;0.05 vs. same group at 4 weeks post TAC,§P&lt;0.05 vs. TAC moderate of same treatment group at same timepoint, ∥P&lt;0.1 vs. baseline of same group and control at same time point, #P&lt;0.1 vs. TAC LNA control of same group at same time point.</p